diff --git a/src/net/torvald/terrarum/TitleScreen.kt b/src/net/torvald/terrarum/TitleScreen.kt
index d026ed609..c03329255 100644
--- a/src/net/torvald/terrarum/TitleScreen.kt
+++ b/src/net/torvald/terrarum/TitleScreen.kt
@@ -366,7 +366,7 @@ class TitleScreen(batch: SpriteBatch) : IngameInstance(batch) {
         }
     }
 
-    private class CameraPlayer(val demoWorld: GameWorld, override val ai: ActorAI) : ActorWithBody(RenderOrder.FRONT, usePhysics = false), AIControlled {
+    private class CameraPlayer(val demoWorld: GameWorld, override val ai: ActorAI) : ActorWithBody(RenderOrder.FRONT, physProp = PhysProperties.MOBILE_OBJECT), AIControlled {
 
         override val hitbox = Hitbox(0.0, 0.0, 2.0, 2.0)
 
diff --git a/src/net/torvald/terrarum/gameactors/ActorWithBody.kt b/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
index d809e4d18..2007cffe8 100644
--- a/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
+++ b/src/net/torvald/terrarum/gameactors/ActorWithBody.kt
@@ -31,7 +31,7 @@ import java.util.*
  *
  * Created by minjaesong on 2016-01-13.
  */
-open class ActorWithBody(renderOrder: RenderOrder, val immobileBody: Boolean = false, var usePhysics: Boolean = true) :
+open class ActorWithBody(renderOrder: RenderOrder, val physProp: PhysProperties) :
         Actor(renderOrder) {
 
 
@@ -389,7 +389,7 @@ open class ActorWithBody(renderOrder: RenderOrder, val immobileBody: Boolean = f
                 isNoSubjectToFluidResistance = isNoClip
             }
 
-            if (!usePhysics) {
+            if (!physProp.usePhysics) {
                 isNoCollideWorld = true
                 isNoSubjectToFluidResistance = true
                 isNoSubjectToGrav = true
@@ -1154,7 +1154,7 @@ open class ActorWithBody(renderOrder: RenderOrder, val immobileBody: Boolean = f
     }
 
     private fun getTileFriction(tile: Int) =
-            if (immobileBody && tile == Block.AIR)
+            if (physProp.immobileBody && tile == Block.AIR)
                 BlockCodex[Block.AIR].friction.frictionToMult().div(500)
                         .times(if (!grounded) elasticity else 1.0)
             else
diff --git a/src/net/torvald/terrarum/gameactors/PhysProperties.kt b/src/net/torvald/terrarum/gameactors/PhysProperties.kt
new file mode 100644
index 000000000..4badf82c2
--- /dev/null
+++ b/src/net/torvald/terrarum/gameactors/PhysProperties.kt
@@ -0,0 +1,33 @@
+package net.torvald.terrarum.gameactors
+
+data class PhysProperties(
+        val immobileBody: Boolean,
+        var usePhysics: Boolean,
+        val useStairs: Boolean
+) {
+    companion object {
+        val HUMANOID_DEFAULT = PhysProperties(
+                immobileBody = false,
+                usePhysics = true,
+                useStairs = true
+        )
+        /** e.g. dropped items, balls */
+        val PHYSICS_OBJECT = PhysProperties(
+                immobileBody = false,
+                usePhysics = true,
+                useStairs = false
+        )
+        /** e.g. voice maker */
+        val IMMOBILE = PhysProperties(
+                immobileBody = true,
+                usePhysics = false,
+                useStairs = false
+        )
+        /** e.g. camera */
+        val MOBILE_OBJECT = PhysProperties(
+                immobileBody = false,
+                usePhysics = false,
+                useStairs = false
+        )
+    }
+}
\ No newline at end of file
diff --git a/src/net/torvald/terrarum/modulebasegame/BuildingMaker.kt b/src/net/torvald/terrarum/modulebasegame/BuildingMaker.kt
index a18805ef1..9525e97a3 100644
--- a/src/net/torvald/terrarum/modulebasegame/BuildingMaker.kt
+++ b/src/net/torvald/terrarum/modulebasegame/BuildingMaker.kt
@@ -134,7 +134,7 @@ class BuildingMaker(batch: SpriteBatch) : IngameInstance(batch) {
 
     val blockMarkings = CommonResourcePool.getAsTextureRegionPack("blockmarkings_common")
     internal var showSelection = true
-    val blockPointingCursor = object : ActorWithBody(Actor.RenderOrder.OVERLAY, usePhysics = false) {
+    val blockPointingCursor = object : ActorWithBody(Actor.RenderOrder.OVERLAY, physProp = PhysProperties.MOBILE_OBJECT) {
 
         override var referenceID: ActorID = 1048575 // custom refID
         override val hitbox = Hitbox(0.0, 0.0, 16.0, 16.0)
@@ -175,7 +175,7 @@ class BuildingMaker(batch: SpriteBatch) : IngameInstance(batch) {
 
     private var _testMarkerDrawCalls = 0L
 
-    private fun generateNewBlockMarkerVisible(x: Int, y: Int) = object : ActorWithBody(Actor.RenderOrder.OVERLAY, usePhysics = false) {
+    private fun generateNewBlockMarkerVisible(x: Int, y: Int) = object : ActorWithBody(Actor.RenderOrder.OVERLAY, physProp = PhysProperties.MOBILE_OBJECT) {
         override var referenceID: ActorID = blockPosToRefID(x, y) // custom refID
         override val hitbox = Hitbox(x * 16.0, y * 16.0, 16.0, 16.0)
 
@@ -543,7 +543,7 @@ class BuildingMakerController(val screen: BuildingMaker) : InputAdapter() {
     }
 }
 
-class MovableWorldCamera(val parent: BuildingMaker) : ActorHumanoid(0, usePhysics = false) {
+class MovableWorldCamera(val parent: BuildingMaker) : ActorHumanoid(0, physProp = PhysProperties.MOBILE_OBJECT) {
 
     init {
         referenceID = Terrarum.PLAYER_REF_ID
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt
index 404e0e5cf..8de8779b0 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/ActorHumanoid.kt
@@ -31,8 +31,8 @@ import java.util.*
 open class ActorHumanoid(
         birth: Long,
         death: Long? = null,
-        usePhysics: Boolean = true
-) : ActorWithBody(RenderOrder.MIDDLE, usePhysics = usePhysics), Controllable, Pocketed, Factionable, Luminous, LandHolder, HistoricalFigure {
+        physProp: PhysProperties = PhysProperties.HUMANOID_DEFAULT
+) : ActorWithBody(RenderOrder.MIDDLE, physProp = physProp), Controllable, Pocketed, Factionable, Luminous, LandHolder, HistoricalFigure {
 
     private val world: GameWorld?
         get() = Terrarum.ingame?.world
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/CreatureBuilder.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/CreatureBuilder.kt
index 337688c2a..5ba099017 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/CreatureBuilder.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/CreatureBuilder.kt
@@ -3,6 +3,7 @@ package net.torvald.terrarum.modulebasegame.gameactors
 import net.torvald.terrarum.gameactors.AVKey
 import net.torvald.terrarum.gameactors.Actor
 import net.torvald.terrarum.gameactors.ActorWithBody
+import net.torvald.terrarum.gameactors.PhysProperties
 import net.torvald.terrarum.gameworld.GameWorld
 
 
@@ -16,7 +17,7 @@ object CreatureBuilder {
      * @Param jsonFileName with extension
      */
     operator fun invoke(module: String, jsonFileName: String): ActorWithBody {
-        val actor = ActorWithBody(Actor.RenderOrder.MIDDLE)
+        val actor = ActorWithBody(Actor.RenderOrder.MIDDLE, physProp = PhysProperties.HUMANOID_DEFAULT)
         InjectCreatureRaw(actor.actorValue, module, jsonFileName)
 
 
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/DroppedItem.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/DroppedItem.kt
index d75cac245..79ecc61e5 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/DroppedItem.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/DroppedItem.kt
@@ -4,13 +4,14 @@ import com.badlogic.gdx.graphics.g2d.SpriteBatch
 import net.torvald.terrarum.blockproperties.BlockCodex
 import net.torvald.terrarum.gameactors.AVKey
 import net.torvald.terrarum.gameactors.ActorWithBody
+import net.torvald.terrarum.gameactors.PhysProperties
 import net.torvald.terrarum.gameitem.GameItem
 import net.torvald.terrarum.itemproperties.ItemCodex
 
 /**
  * Created by minjaesong on 2016-03-15.
  */
-open class DroppedItem(private val item: GameItem) : ActorWithBody(RenderOrder.MIDTOP) {
+open class DroppedItem(private val item: GameItem) : ActorWithBody(RenderOrder.MIDTOP, PhysProperties.PHYSICS_OBJECT) {
 
     init {
         if (item.dynamicID >= ItemCodex.ACTORID_MIN)
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/FixtureBase.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/FixtureBase.kt
index 67dfc9eff..5ea16af02 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/FixtureBase.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/FixtureBase.kt
@@ -6,6 +6,7 @@ import net.torvald.terrarum.Terrarum
 import net.torvald.terrarum.blockproperties.Block
 import net.torvald.terrarum.blockproperties.BlockCodex
 import net.torvald.terrarum.gameactors.ActorWithBody
+import net.torvald.terrarum.gameactors.PhysProperties
 import net.torvald.terrarum.gameworld.GameWorld
 import net.torvald.terrarum.ui.UICanvas
 
@@ -19,7 +20,7 @@ open class FixtureBase(
         val mainUI: UICanvas? = null
 
 // disabling physics (not allowing the fixture to move) WILL make things easier in many ways
-) : ActorWithBody(renderOrder, immobileBody = true, usePhysics = false), CuedByTerrainChange {
+) : ActorWithBody(renderOrder, PhysProperties.IMMOBILE), CuedByTerrainChange {
 
     var blockBox: BlockBox = blockBox0
         protected set // something like TapestryObject will want to redefine this
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/HumanoidNPC.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/HumanoidNPC.kt
index d6ecbaf1c..f01e52aa0 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/HumanoidNPC.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/HumanoidNPC.kt
@@ -14,10 +14,9 @@ import net.torvald.terrarum.itemproperties.Material
  */
 open class HumanoidNPC(
         override val ai: ActorAI, // it's there for written-in-Kotlin, "hard-wired" AIs
-        born: Long,
-        usePhysics: Boolean = true
+        born: Long
         //forceAssignRefID: Int? = null
-) : ActorHumanoid(born, usePhysics = usePhysics), AIControlled, CanBeAnItem {
+) : ActorHumanoid(born), AIControlled, CanBeAnItem {
 
     companion object {
         val DEFAULT_COLLISION_TYPE = COLLISION_DYNAMIC
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestBall.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestBall.kt
index 8d5d1663f..d4087524d 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestBall.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestBall.kt
@@ -4,12 +4,13 @@ import com.badlogic.gdx.graphics.Color
 import com.badlogic.gdx.graphics.g2d.SpriteBatch
 import net.torvald.terrarum.Terrarum
 import net.torvald.terrarum.gameactors.ActorWithBody
+import net.torvald.terrarum.gameactors.PhysProperties
 import net.torvald.terrarum.modulebasegame.worldgenerator.RoguelikeRandomiser
 
 /**
  * Created by minjaesong on 2016-03-05.
  */
-class PhysTestBall : ActorWithBody(RenderOrder.MIDDLE, immobileBody = true) {
+class PhysTestBall : ActorWithBody(RenderOrder.MIDDLE, PhysProperties.PHYSICS_OBJECT) {
 
     private var color = Color.GOLD
 
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestLuarLander.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestLuarLander.kt
index be98ddf89..65f2277fa 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestLuarLander.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/PhysTestLuarLander.kt
@@ -11,7 +11,7 @@ import net.torvald.terrarum.gameactors.*
 /**
  * Created by minjaesong on 2018-01-17.
  */
-class PhysTestLuarLander : ActorWithBody(RenderOrder.MIDTOP), Controllable {
+class PhysTestLuarLander : ActorWithBody(RenderOrder.MIDTOP, PhysProperties.PHYSICS_OBJECT), Controllable {
 
     private val texture = Texture(ModMgr.getGdxFile("basegame", "sprites/phystest_lunarlander.tga"))
 
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/ProjectileSimple.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/ProjectileSimple.kt
index 433a2dcf7..c2afe3777 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/ProjectileSimple.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/ProjectileSimple.kt
@@ -10,6 +10,7 @@ import net.torvald.terrarum.blockproperties.BlockCodex
 import net.torvald.terrarum.gameactors.ActorWithBody
 import net.torvald.terrarum.gameactors.Hitbox
 import net.torvald.terrarum.gameactors.Luminous
+import net.torvald.terrarum.gameactors.PhysProperties
 import org.dyn4j.geometry.Vector2
 import java.util.*
 
@@ -24,7 +25,7 @@ open class ProjectileSimple(
         private val type: Int,
         fromPoint: Vector2, // projected coord
         toPoint: Vector2    // arriving coord
-) : ActorWithBody(RenderOrder.MIDTOP), Luminous, Projectile {
+) : ActorWithBody(RenderOrder.MIDTOP, PhysProperties.PHYSICS_OBJECT), Luminous, Projectile {
 
     val damage: Int
     val displayColour: Color
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/WeaponSwung.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/WeaponSwung.kt
index 758704d44..7920fd643 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/WeaponSwung.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/WeaponSwung.kt
@@ -4,11 +4,12 @@ import net.torvald.gdx.graphics.Cvec
 import net.torvald.terrarum.gameactors.ActorWithBody
 import net.torvald.terrarum.gameactors.Hitbox
 import net.torvald.terrarum.gameactors.Luminous
+import net.torvald.terrarum.gameactors.PhysProperties
 
 /**
  * Created by minjaesong on 2016-04-26.
  */
-class WeaponSwung(val itemID: Int) : ActorWithBody(RenderOrder.MIDTOP), Luminous {
+class WeaponSwung(val itemID: Int) : ActorWithBody(RenderOrder.MIDTOP, PhysProperties.IMMOBILE), Luminous {
     // just let the solver use AABB; it's cheap but works just enough
 
     /**
diff --git a/src/net/torvald/terrarum/modulebasegame/gameactors/physicssolver/CollisionSolver.kt b/src/net/torvald/terrarum/modulebasegame/gameactors/physicssolver/CollisionSolver.kt
index 169f12107..b01d05e0b 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameactors/physicssolver/CollisionSolver.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameactors/physicssolver/CollisionSolver.kt
@@ -40,7 +40,7 @@ object CollisionSolver {
 
         // mark list x
         (Terrarum.ingame!! as TerrarumIngame).actorContainerActive.forEach { it ->
-            if (it is ActorWithBody && it.usePhysics) {
+            if (it is ActorWithBody && it.physProp.usePhysics) {
                 collListX.add(CollisionMarkings(it.hitbox.hitboxStart.x, STARTPOINT, it))
                 collListX.add(CollisionMarkings(it.hitbox.hitboxEnd.x, ENDPOINT, it))
             }
@@ -73,7 +73,7 @@ object CollisionSolver {
 
         // mark list y
         (Terrarum.ingame!! as TerrarumIngame).actorContainerActive.forEach { it ->
-            if (it is ActorWithBody && it.usePhysics) {
+            if (it is ActorWithBody && it.physProp.usePhysics) {
                 collListY.add(CollisionMarkings(it.hitbox.hitboxStart.y, STARTPOINT, it))
                 collListY.add(CollisionMarkings(it.hitbox.hitboxEnd.y, ENDPOINT, it))
             }
diff --git a/src/net/torvald/terrarum/modulebasegame/gameitems/BlockBase.kt b/src/net/torvald/terrarum/modulebasegame/gameitems/BlockBase.kt
index cd78e8f1b..345a8db2f 100644
--- a/src/net/torvald/terrarum/modulebasegame/gameitems/BlockBase.kt
+++ b/src/net/torvald/terrarum/modulebasegame/gameitems/BlockBase.kt
@@ -35,7 +35,7 @@ object BlockBase {
         if (gameItem.inventoryCategory == GameItem.Category.BLOCK) {
             var ret1 = true
             ingame.actorContainerActive.forEach {
-                if (it is ActorWithBody && it.usePhysics && it.intTilewiseHitbox.intersects(mousePoint))
+                if (it is ActorWithBody && it.physProp.usePhysics && it.intTilewiseHitbox.intersects(mousePoint))
                     ret1 = false // return is not allowed here
             }
             if (!ret1) return ret1
diff --git a/work_files/physics_staircasing.kra b/work_files/physics_staircasing.kra
new file mode 100644
index 000000000..3a2046800
Binary files /dev/null and b/work_files/physics_staircasing.kra differ